This invention is directed to a drive circuit for applying drive signals to a temperature dependent liquid crystal display cell and in particular to a feedback control circuit including a temperature dependent reference voltage element for effecting adjustment of a drive signal in accordance with the temperature dependency characteristic of the display cell.
While digital displays have taken on various forms, the low power consumption characteristic of liquid crystal display cells has caused same to be most often selected for use in devices requiring a digital display. Specifically, in table calculators, pocket calculators, electronic timepieces and particularly electronic wristwatches, the low power consumption characteristic of the liquid crystal display elements is particularly desirable in view of the effect that same has on lengthening the life of a battery power source.
Such liquid crystal display elements are driven by a stable DC drive voltage at a particular temperature. Nevertheless, liquid crystal display cells have a temperature dependency characteristic which causes the voltage required to energize same to decrease in response to a corresponding increase in temperature. Although drive circuits have been provided for applying a uniformly stable DC drive voltage to the liquid crystal display cell, such drive circuits have been less than completely satisfactory due to their failure to compensate for the temperature dependency characteristic of the display cell.
Accordingly, a drive circuit particularly adapted to effect a reduction in the DC drive voltage applied to a liquid crystal display cell corresponding to the decrease in the voltage required to drive such a liquid crystal display element in response to a rise in the temperature thereof is desired.